1. Field of the Invention
This invention relates to error detection circuits and, more particularly, to a novel and highly-effective error detection circuit that requires no error correcting code and is suitable for use with digital signal reproducing apparatus, for example a digital video tape player.
2. Description of the Prior Art
In a digital video tape recorder (VTR) for recording and/or reproducing a composite color video signal as a digital signal, erroneous data occurring in a normal playback mode can be detected by means of error detecting or correcting codes. In practice, the error is corrected when error correction is possible by means of the error correcting code and is concealed by interpolation using mean values or the like when the error is not correctable.
In the variable-speed playback mode, however, the rotary head scans at an angle across a plurality of tracks because of the changes in the tape speed and therefore it becomes impossible to obtain continuous accurate data. Thus, error correction by means of an error correcting code is considered generally difficult. Although error correction codes of small code length can be used so that error can be corrected also during the variable-speed playback, there arises the problem that the correct video data is not utilized when the redundant code as its error correcting code is incorrect, since the interleave length of the correcting code is short. Further, since the error rate increases in the variable-speed playback mode, there occurs another problem that proper correction cannot be made when error correction is performed based on the detected result of error correcting codes